JP4848506B2 - Plastic disassembly method - Google Patents

Description

  The invention relates in particular to a method for decomposing plastics containing unsaturated polyester resins suitable for FRP (fiber reinforced plastics).

  Plastics are lightweight, high-strength, strong against rust and corrosion, free to color, excellent in electrical insulation, easy to mold, and capable of mass production. It is used in large quantities as materials for household goods. For this reason, the amount of waste plastic continues to increase.

Conventionally, most of the waste plastic has been disposed of by landfill or incineration. However, when waste plastic is landfilled, the ground after landfill becomes unstable, causing a problem that it is difficult to secure land for landfill. In addition, when waste plastic is incinerated, harmful gases (for example, CO ₂ ) and bad odors are generated, which not only causes concern about environmental pollution, but also causes a problem that the incinerator is damaged.

  Therefore, the Containers and Packaging Waste Law (Recycling Law) was enacted in 1995, and waste plastics were collected and required to be reused. With the enforcement of this law, technological development for recycling waste plastics is rapidly progressing.

  For example, a method for recovering an oily substance obtained by thermally decomposing waste plastic using supercritical water as a reaction medium is disclosed (see Patent Document 1).

In addition, after crushing the cured unsaturated polyester resin, which is waste plastic, the decomposition product obtained by decomposing with dicarboxylic acid or diamine at a temperature of about 100 ° C. to 300 ° C. is reused as a resin raw material. A method of re-synthesizing is also disclosed (see Patent Document 2).
Japanese Patent Laid-Open No. 10-67991 Japanese Patent Laid-Open No. 9-221565

  However, if the waste plastic is pyrolyzed using the supercritical method described in Patent Document 1 described above, the treatment temperature is too high, so that the main chains and side chains in the waste plastic are cleaved randomly and the resulting oily oil is obtained. Many kinds of low molecular weight components were contained in the substance. The oily substance obtained by pyrolyzing waste plastic is mainly reused as a liquid fuel. However, in order to ensure the quality of the oily substance after pyrolysis, the oily substance is treated with a catalyst (for example, , Zeolite) must be modified and post-treatment is required, which has been a factor in increasing the treatment cost. Further, even when the reforming process is performed, it is difficult to reuse the reformed product oil as a petroleum product (for example, kerosene or light oil) itself.

  Further, in the method described in Patent Document 2, the obtained decomposition product can be reused as an unsaturated polyester resin raw material. However, when the cured unsaturated plastic is decomposed at a high temperature exceeding 280 ° C., thermal decomposition is not possible. It has progressed and has a problem that the strength of the thermosetting resin is lowered when re-cured. Furthermore, even when the temperature during decomposition was a low temperature of about 100 ° C. to 180 ° C., the recovery rate of the resin raw material that can be recovered after thermal decomposition was low. For these reasons, the proportion of the recovered raw resin that is re-cured and used as a product is low.

The present invention has been made in order to solve the above-described problems. That is, the plastic decomposition method of the present invention uses a plastic containing an unsaturated polyester resin formed from an unsaturated polyester portion and a crosslinked portion. Copolymer of polyhydric alcohol and organic acid, which is a raw material monomer of unsaturated polyester resin, and styrene and fumaric acid, by pyrolysis using alkali-containing subcritical water whose temperature is lower than the thermal decomposition temperature of saturated polyester resin The aqueous solution obtained after decomposition was charged with an acid to adjust the pH to 6 to 9, and in the resulting aqueous solution , methanol, ethanol, and a raw material monomer of the unsaturated polyester resin. and there polyhydric alcohol selected from the group mixed by introducing consisting alcohol, solids of the copolymer of the styrene and fumaric acid, polyhydric alcohol Le and separated into an aqueous solution containing the organic acid and water were removed contained in the separated aqueous solution, and summarized in that to obtain a polyhydric alcohol and an organic acid.

  According to the method for decomposing a plastic of the present invention, a compound of an organic acid, a polyhydric alcohol, and an organic acid, which are resin raw materials, can be recovered in a high yield, and the physical properties of the recovered resin raw material are hardly deteriorated again. Equivalent plastic can be recycled. As a result, waste plastic can be recycled and effectively used.

  Hereinafter, a plastic disassembling method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  An FRP (fiber reinforced plastic) decomposition method using the plastic decomposition method according to the embodiment of the present invention will be described with reference to FIG.

  First, as shown in FIG. 1, a plastic 1 containing an unsaturated polyester resin formed from an unsaturated polyester portion and a crosslinked portion is hydrolyzed using subcritical water whose temperature is lower than the thermal decomposition temperature of the unsaturated polyester resin. (Step A). When decomposed, an aqueous solution 2 is obtained. In the aqueous solution 2, a polyhydric alcohol 3 (for example, glycol) and an organic acid 4 (for example, fumaric acid), which are raw materials for the unsaturated polyester resin, and an unsaturated polyester resin are used. And a compound 5 of the organic acid (for example, styrene fumarate: a copolymer of styrene and fumaric acid).

Next, an alcohol is added to the obtained aqueous solution 2 (step B), followed by filtration to obtain an aqueous solution 6 containing a polyhydric alcohol 3 and an organic acid 4, and a solid of an organic acid compound 5. To separate. Alcohol has relatively low compatibility with the organic acid compound 5 and is hardly soluble, and has high compatibility with water. Therefore, when the alcohol is added to the aqueous solution 2 and mixed, the solution 2 and the organic acid compound 5 are mixed. And the aqueous solution 6 containing the polyhydric alcohol 3 and the organic acid 4 and the solid matter of the organic acid compound 5 can be separated.

  Finally, water contained in the separated aqueous solution 6 is removed (step C) to obtain the polyhydric alcohol 3 and the organic acid 4.

  In general, when decomposing plastics made from raw materials containing polyhydric alcohols and organic acids, thermosetting plastics cannot be decomposed in a low temperature (about 100 ° C) environment, and the thermoplastics are decomposed. In order to achieve this, a processing time of several tens of hours was required and the reaction was long. On the other hand, when plastic is decomposed under high temperature (about 360 ° C) and high pressure (about 20MPa), as in the case of using critical water (critical temperature 374.4 ° C, critical pressure 22.1MPa), Since the next decomposition occurs and there is a concern about the corrosion of the apparatus, it is difficult to decompose the raw material monomer in a high yield with the unit of the raw material monomer of the resin. According to the decomposition method of the above, by decomposing using the subcritical water (below 280 ° C, 7MPa or less) below the thermal decomposition temperature of the unsaturated polyester resin, the raw material monomer of the unsaturated polyester resin is decomposed. In addition, the raw material monomer can be recovered in a high yield.

  In the above plastic decomposition method, if the alcohol to be added after decomposition with subcritical water is a solvent lower than the boiling point of water, the concentration in the subsequent step C is facilitated and the processing speed is improved, and only the alcohol is fractionated. It is preferable in that it can be easily reused because it is easy to recycle, and examples thereof include methanol and ethanol. The amount of alcohol to be added is not particularly limited, but is preferably equal to or more than the weight of the aqueous solution when the plastic is decomposed with subcritical water. On the other hand, when a solvent having a boiling point higher than the boiling point of water is used for the alcohol introduced after decomposition with subcritical water, the inorganic substance dissolved in the water is removed by heating the aqueous solution separated after the addition of the alcohol to remove only water. Is preferable in that these inorganic substances can be easily removed. For example, propylene glycol can be mentioned. The amount of alcohol input in this case is not particularly limited, but is preferably equal to or more than the weight of the aqueous solution when the plastic is decomposed with subcritical water.

  Furthermore, when the subcritical water is a solution containing an alkali, it is preferable to precipitate the alkali contained in the subcritical water as a salt for separation. As a method for separating the salt, the following two methods may be mentioned.

  In one method, an acid (for example, HCl) is added to an aqueous solution obtained after decomposition with subcritical water to adjust the pH to 6 to 9, and then an alcohol is added. In this method, alcohol is added to a concentrated solution obtained by removing a solvent (water, alcohol), a salt is precipitated, and then the salt is separated to obtain a polyhydric alcohol and an organic acid. In this method, when an alcohol to be introduced after decomposition with subcritical water is introduced, a solvent having a boiling point higher than the boiling point of water (for example, propylene glycol) is introduced. The alcohol is still present. For this reason, it is not necessary to add the alcohol for salt precipitation again in the concentrated liquid from which water has been removed.

  Another method is similar to the first method, in which an acid is added to the aqueous solution obtained after decomposition to adjust the pH to 6 to 9, and then an alcohol is added. Further, in the separated aqueous solution, In this method, after removing the alcohol, the salt is separated from the obtained aqueous solution using a reverse osmosis membrane to obtain a polyhydric alcohol and an organic acid. As a reverse osmosis membrane to be used, it is preferable to use a membrane made of polyamide or polyvinyl alcohol because it has high wettability with an aqueous solution to be filtered and is easy to filter.

In the two methods described above, the alcohol used for salting out precipitation is related to the synthesis reaction when the obtained polyhydric alcohol is reused when the same polyhydric alcohol as the raw material monomer of the plastic is used. Alcohol free separation / removal etc. is unnecessary, which is preferable.

  Further, a method for decomposing FRP using the plastic decomposing method according to the embodiment of the present invention will be described in detail with reference to FIG.

  First, 600 g of FRP (containing 34 wt% of propylene glycol-maleic anhydride-styrene copolymer, glass fiber and 66 wt% of calcium carbonate as a filler) pulverized under 1.7 mm is prepared.

  Next, as shown in FIG. 2 (a), FRPa 600g, calcium hydroxide b (Nacalai Tesque) 100 g) and pure water c1800 g are added, and the lid 11 of the heat-resistant container 1 is closed.

  Thereafter, as shown in FIG. 2 (b), it is heated at 230 ° C. for 120 minutes and decomposed with subcritical water. After cooling to room temperature, solid-liquid separation is performed using a glass filter (GC-25, manufactured by Advantech Toyo Co., Ltd.). As shown in FIG. 2 (c), the separated solid is an inorganic substance d of glass fiber and calcium carbonate, and the inorganic substance d is recovered and reused as an inorganic filler. The aqueous solution e from which the inorganic substance d has been removed contains decomposed glycol, fumaric acid, and styrene fumarate (styrene / fumaric acid copolymer).

  Next, as shown in FIG. 2 (d), 1N HClf is added to the aqueous solution e from which the inorganic substance d has been removed to adjust the pH to 6-9. Further, as shown in FIG. 2 (e), the aqueous solution Methanol g twice as much as e is added to the aqueous solution e, and the resulting aqueous solution e ′ is filtered.

  After filtration, styrene fumarate h is recovered as shown in FIG. The recovered styrene fumarate h has the molecular structure shown in FIG. 3 and is reused as a resin raw material. On the other hand, the filtrate i from which the styrene fumarate h has been removed is heated to remove methanol and water as solvents, and concentrated to about 1/10 of the amount of water used during subcritical water decomposition. Then, it cools to room temperature.

  Further, as shown in FIG. 2 (g), methanol k is added to the concentrated concentrate j. Then, the solubility of the salt dissolved in the concentrated liquid j is lowered, and the salt is precipitated.

  After salt precipitation, glycol m and fumaric acid n are recovered as shown in FIG. 2 (h).

  Further, when the reverse osmosis membrane is used when the alkali contained in the subcritical water is separated as a salt, the method shown in FIG. 4 is used. Since the steps up to the step shown in FIG. 2 (f) are the same, the same reference numerals are used and the description thereof is omitted.

  As shown in FIG. 4 (f), the filtrate i from which the styrene fumarate h has been removed is heated at a boiling point of methanol or higher and below the boiling point of water to remove methanol from the filtrate i. Then, it is set as the aqueous solution concentrated to about 1/10 of the amount of water used at the time of decomposition | disassembly by subcritical water, and this aqueous solution is cooled to room temperature.

  Next, as shown in FIG. 4 (g), the cooled aqueous solution l is incorporated into the cross flow module 12 and allowed to pass through a spiral type membrane (outer shape 2 inches) made of polyvinyl alcohol. The water flow conditions were a pressure of 1.5 MPa and a flow rate of 5 L / min. The salt is separated by filtration to recover glycol m and fumaric acid n.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
In Example 1, FRP was decomposed | disassembled using the decomposition | disassembly method of the fiber reinforced plastic shown in FIG. The materials and reaction conditions used were the same as those described in FIG. 2, and methanol was used as an alcohol having a boiling point lower than that of water when recovering styrene fumarate. In Example 1, since alkali is not contained in subcritical water, the process which isolate | separates a salt is not carried out.

  Recovered amounts of styrene fumarate, glycol and fumaric acid recovered from Example 1 were measured. Moreover, the recovery rate was calculated from each recovery amount of glycol and fumaric acid. First, the concentration of glycol was measured with a gas chromatograph analyzer, and the concentration of fumaric acid was measured with an ion chromatograph device. Thereafter, the concentration of the measured glycol and fumaric acid was multiplied by the sample amount, and the calculation was performed based on the following formulas 1 and 2.

[Formula 1] Glycol recovery rate (%) = recovered glycol amount (g) / (amount of FRP resin used x glycol blending ratio)
[Formula 2] Recovery rate of fumaric acid (%) = Fumaric acid recovered amount (g) / (FRP resin used × Fumaric acid content ratio)
The amount of FRP resin used was 600 (g), the proportion of resin in FRP was 34 wt%, and the proportion of glycol and fumaric acid blended in the resin was 23 wt% when the resin part was 100 wt%. is there. Therefore, FRP resin amount x glycol blending ratio is 600 (g) x 0.34 (wt%) x 0.23 (wt%), FRP resin amount x fumaric acid blending ratio is 600 (g) x 0.34 (wt%) x 0.23 ( wt%).

The results of the recovery amount and recovery rate are shown in Table 1.

(Example 2)
In Example 2, FRP was decomposed using the plastic decomposition method shown in FIG. Using the same method as in Example 1, the recovered amount and recovery rate of styrene fumarate, glycol and fumaric acid recovered from Example 2 were determined, and the results are shown in Table 1.

(Example 3)
In Example 3, propylene glycol having a boiling point higher than that of water was used as the alcohol to be added after decomposition with subcritical water using the plastic decomposition method shown in FIG. The recovered amounts of styrene fumarate, glycol and fumaric acid recovered from Example 3 were measured, and the recovery rate of fumaric acid was calculated using the same method as in Example 1. In addition, the recovery rate of glycol calculated the weight increase with respect to the added glycol amount, and calculated | required the recovery rate from this increase. The results of the recovery amount and recovery rate are shown in Table 1.

(Comparative Example 1-1)
In Comparative Example 1-1, hexane was used instead of methanol, and FRP was decomposed under the same conditions as in Example 1. Using the same method as in Example 1, the recovered amount and recovery rate of styrene fumarate, glycol and fumaric acid recovered from Comparative Example 1-1 were determined, and the results are shown in Table 1.

(Comparative Example 1-2)
In Comparative Example 1-2, acetone was used instead of methanol, and FRP was decomposed under the same conditions as in Example 1. Using the same method as in Example 1, the recovered amount and recovery rate of styrene fumarate, glycol and fumaric acid recovered from Comparative Example 1-2 were determined, and the results are shown in Table 1.

(Comparative Example 2-1)
In Comparative Example 2-1, acetone was used instead of methanol, and FPR was decomposed under the same conditions as in Example 2. Using the same method as in Example 1, the recovered amounts and recovery rates of styrene fumarate, glycol and fumaric acid recovered from Comparative Example 2-1 were determined, and the results are shown in Table 1.

(Comparative Example 2-2)
In Comparative Example 2-2, tetrahydrofuran was used instead of methanol, and FPR was decomposed under the same conditions as in Example 2. Using the same method as in Example 1, the recovered amount and recovery rate of styrene fumarate, glycol and fumaric acid recovered from Comparative Example 2-2 were determined, and the results are shown in Table 1.

Example 4
In Example 4, FRP was decomposed using the plastic decomposition method shown in FIG. The recovered amount of styrene fumarate recovered from Example 4 was determined and shown in Table 2. Further, the recovery amount and recovery rate of glycol and fumaric acid contained in each of the concentrate and the permeate obtained from Example 4 were determined using the same method as in Example 1. Furthermore, in order to confirm whether the deposited salt was removed with a reverse osmosis membrane made of polyvinyl alcohol, the evaporation residue of the concentrate and the permeate was measured. These results are shown in Table 2.

  From the results of Examples and Comparative Examples, as shown in Table 1, in Examples 1 to 3 in which alcohol was added after decomposition with subcritical water, the resin component recovery rate showed a value of 80% or more. The resin component recovery rate was higher than that of the comparative example in which a solvent other than alcohol was added. Among the recovered resin components, the recovery amount of styrene fumarate was particularly increased. Further, when Example 1 in which methanol lower than the boiling point of water was added as alcohol and Example 3 in which propylene glycol higher than the boiling point of water was compared was compared, recovery of styrene fumarate and glycol in Example 1 was compared. The amount increased, and it was found that when methanol was added compared to propylene glycol, the overall resin component recovery rate increased. The reason why the recovery rate of the comparative example in which a solvent other than alcohol is added is low is that hexane and tetrahydrofuran are poorly soluble or slightly soluble in water, so the compatibility of the aqueous solution with styrene fumarate cannot be reduced. It is estimated that the recovery rate was reduced due to a decrease in separability. On the other hand, acetone is compatible with water, but also compatible with styrene fumarate. Since it cannot be lowered, it is estimated that the separability is lowered and the recovery rate is lowered.

  Moreover, as shown in Table 2, even when methanol was added after decomposition with subcritical water and the salt was removed by a reverse permeable membrane made of polyvinyl alcohol, the resin component recovery rate showed a value of 80% or more. . Furthermore, the amount of evaporation residue in the concentrate increased compared to the amount of evaporation residue in the permeate, and it was found that salt can be effectively removed by using a reverse permeable membrane.

  As a result, it was found that styrene fumarate, fumaric acid, and glycol, which can be reused again as a raw material for FRP, can be recovered in high yield using FRP. For this reason, according to the plastic disassembling method according to the embodiment of the present invention, the waste plastic can be recycled and effectively used.

It is a figure explaining the decomposition | disassembly method of FRP using the decomposition method of the plastic which concerns on embodiment of this invention. It is a figure explaining the method of decomposing | disassembling FRP using the plastic decomposition method which concerns on embodiment of this invention, and is a figure which shows the method in the case of depositing and isolate | separating the alkali contained in subcritical water as a salt. . It is a figure which shows the molecular structure of the styrene fumarate collect | recovered by the method of decomposing | disassembling FRP using the decomposition method of the plastic concerning embodiment of this invention. It is a figure which shows the method in the case of using a reverse osmosis membrane when depositing and isolate | separating the alkali contained in subcritical water which concerns on embodiment of this invention as a salt.

Explanation of symbols

1 ... Plastic containing unsaturated polyester resin,
2 ... aqueous solution (including polyhydric alcohol 3, organic acid 4 and organic acid compound 5),
3 ... polyhydric alcohol,
4 ... Organic acid,
5 ... Organic acid compound,
6 ... aqueous solution (including polyhydric alcohol 3 and organic acid 4),

Claims (7)

A plastic containing an unsaturated polyester resin formed from an unsaturated polyester part and a crosslinked part is decomposed using subcritical water containing alkali having a temperature lower than the thermal decomposition temperature of the unsaturated polyester resin, and the unsaturated An aqueous solution containing a polyhydric alcohol and an organic acid, which are raw materials for polyester resin, and a copolymer of styrene and fumaric acid,
An acid is added to the aqueous solution obtained after decomposition to adjust the pH to 6 to 9,
Into the obtained aqueous solution, an alcohol selected from the group consisting of methanol, ethanol, and a polyhydric alcohol that is a raw material monomer of the unsaturated polyester resin is added and mixed, and the styrene and fumaric acid co-polymerized. A method for decomposing a plastic, comprising separating a solid product into an aqueous solution containing the polyhydric alcohol and the organic acid.   The method for decomposing a plastic according to claim 1, wherein the alcohol is a solvent lower than the boiling point of water. Furthermore, after adding water into the concentrated solution obtained by removing the water in the separated aqueous solution to precipitate the salt, the salt is separated to obtain a polyhydric alcohol and an organic acid. The method for decomposing plastic according to claim 1 or 2, characterized in that: Furthermore, alcohol in the separated aqueous solution is removed, and a salt is separated from the obtained solution using a reverse osmosis membrane to obtain a polyhydric alcohol and an organic acid. The method for decomposing plastics as described.   5. The method for decomposing a plastic according to claim 4, wherein the reverse osmosis membrane is a membrane made of polyamide or polyvinyl alcohol.   The method for decomposing a plastic according to claim 1, wherein the alcohol is a solvent having a boiling point higher than that of water.   The method for decomposing a plastic according to any one of claims 1 to 6, wherein a polyhydric alcohol which is a raw material monomer of an unsaturated polyester resin is used as the alcohol.

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